identifier: traitmech:000659
label: fungal appressorium formation
definition: A morphological phenotype in which a fungus forms specialized surface-associated
  penetration structures called appressoria.
definition_source: DOI:10.3390/jof5030072
trait_category: MORPHOLOGY
term_kind: CLASS
mapping_status: PROPOSED
parent_traits:
- METPO:1000059
evidence:
- reference: DOI:10.3390/jof5030072
  snippet: Here, we report on the ability of many saprotrophs from a large range of
    taxa to produce appressoria on cellophane.
  notes: Demoor, Silar and Brun (2019), PMID:31382649, PMC6787622; scientific abstract
    retrieved as full-text XML. Introduction, Methods, Results and the broad-definition
    Discussion paragraph were read; actual Figures 2 and 6 and supplementary Table
    S1 were inspected. The authors explicitly include structures previously called
    appressorium-like under a broad penetration-structure usage, including unicellular
    and compound forms. The principal assay used mycelial implants on cellophane over
    M2 medium at 27 C, with observations after 3-15 days. It is not an in-host assay
    or a universal fungal prevalence estimate. Contact and growth reorientation without
    penetration were distinguished from appressoria. Negative results apply to the
    tested conditions, not to entire clades. Table S1 identifies strains but does
    not independently establish natural provenance for all of them; they are not added
    as canonical examples.
- reference: DOI:10.1371/journal.ppat.1002514
  snippet: an appressorium is already developing in Guy11 strain whereas no infection
    cell development occurs in an isogenic Δpmk1 mutant
  notes: Soanes et al. (2012), PMID:22346750, PMC3276559; Results describing Figure
    1B, not the Author Summary. Actual Figure 1 and the fungal-strain/growth Methods
    were inspected. Wild-type Guy11 and the deletion mutant were compared at four
    hours; the Guy11 series also includes 6, 8, 14 and 16 hours. The Methods describe
    plastic coverslips and 1,16-hexadecanediol, whereas the Results describing Figure
    1A name a hydrophobic glass slide. This within-article surface discrepancy is
    unresolved; neither description is silently substituted for the other or treated
    as a universal surface requirement. Natural-isolate provenance is checked separately
    in the canonical-example note. The observed formation phenotype is not inferred
    from RNA expression. Neither these transcript profiles nor one deletion establish
    a universal protein-resolved mechanism across fungi. Other figures and transcript-data
    supplements were not inspected.
- reference: DOI:10.1186/1741-7007-6-9
  snippet: blocking of the cell cycle did not prevent spore germination and appressoria
    formation.
  notes: Nesher, Barhoom and Sharon (2008), PMID:18275611, PMC2276476; scientific
    abstract Results, read directly in full-text XML. The Methods name Colletotrichum
    gloeosporioides f. sp. aeschynomene 3.1.3 wild-type and transgenic strains; germination
    and onion-epidermis assays were read. This result separates formation from a universal
    mitosis requirement. It does not show unrestricted post-penetration growth under
    cell-cycle inhibition. Full result figures, natural strain provenance and current
    species-complex assignment were not inspected or resolved, so this is qualified
    evidence, not a canonical taxon assignment or a universal autophagy/cell-cycle
    claim.
- reference: DOI:10.1111/nph.13931
  snippet: Here we identify an appressorium‐like structure, which we call an expressorium
  notes: Becker et al. (2016), PMID:26991322, PMC5069595; the article's scientific
    Summary and the Results paragraph distinguishing intrinsecus/extrinsecus terminology
    were read directly in full-text XML. The internal structure enables Epichloe festucae
    to exit a leaf. The authors propose expressorium to distinguish it from an external
    appressorium, while noting an intrinsecus-appressorium convention. This is terminology-boundary
    evidence, not an asserted exact synonym or additional canonical example. Figures,
    movies, supplements and strain provenance were not inspected; no Nox mechanism
    or turgor measurement is inferred from this quotation.
canonical_examples:
- taxon_id: NCBITaxon:318829
  taxon_label: Pyricularia oryzae
  reference: DOI:10.1371/journal.ppat.1002514
  note: Wild-type Guy11 in Soanes et al. (2012), Figure 1A-B and Methods, directly
    forms appressoria under the tested in-vitro induction conditions. NCBI Taxonomy
    resolves Pyricularia oryzae at species rank and lists the paper's Magnaporthe
    oryzae name as a synonym. Independent primary population-study Methods at https://doi.org/10.5423/PPJ.NT.04.2013.0042
    (PMID:25288972, PMC4174813) explicitly identify Guy11 as a rice-pathogenic isolate
    from French Guiana and distinguish it from laboratory crossing derivatives. That
    passage was read directly; its cited original 1988 isolation study was not retrieved.
    This provenance citation is not counted as an independent appressorium observation.
    The example concerns Guy11, not its engineered deletion mutant, strain 70-15,
    every strain, or every environmental condition.
discussions:
- discussion_id: fungal-appressorium-scope-and-mapping
  prompt: Reconcile broad appressorium usage and neighboring structures.
  kind: CURATION_TODO
  status: OPEN
  rationale: Retain phenotype METPO:1000059 rather than plant pathogen METPO:1004003,
    black pigmented METPO:1003022 or thigmotropism traitmech:000594. Formation is
    neither disease causation nor generic adhesion or contact-directed growth. Demoor
    et al. (2019) explicitly use a broad appressorium umbrella for saprotrophic penetration
    structures and compound infection cushions; preserve this source attribution rather
    than silently imposing a single-celled, melanized or germ-tube-only definition.
    Becker et al. (2016) distinguish expressoria from external appressoria despite
    the intrinsecus convention. Whether to include that exit structure or propose
    narrower subclasses remains unresolved; no exact synonym is asserted. QuickGO
    resolves GO:0075016 as a host-associated biological process, not an exact organismal
    phenotype covering the saprotrophic observations, so xrefs and SSSOM are omitted.
    Research-report appressorium mentions describe candidate material structures,
    not an existing exact formation-trait node that can simply be regrounded.
  posed_by: codex
  posed_date: '2026-10-07'
- discussion_id: fungal-appressorium-function-and-mechanism
  prompt: Separate formation, functional penetration and regulatory mechanisms.
  kind: KNOWLEDGE_GAP
  status: OPEN
  rationale: Formation does not guarantee successful penetration, host entry, invasion
    or disease. Do not require one shape, cell number, pigmentation, turgor level,
    surface chemistry or nutritional regime. Cellophane penetration is not evidence
    of natural-host infection or of a functional haustorium. The Colletotrichum cell-cycle
    results and the Guy11 Pmk1 comparison do not support a universal mitosis, autophagy
    or kinase dependency. A causal graph awaits review of primary perturbation/complementation
    experiments, remaining figures and supplements, and taxon-paired protein accessions.
    Transcriptional association or possession of a candidate gene is not proof of
    this formation phenotype. Keep the unresolved 3.1.3 provenance/species assignment
    and all unverified survey strains out of canonical examples.
  posed_by: codex
  posed_date: '2026-10-07'
curation_history:
- timestamp: '2026-10-07T05:29:43Z'
  curator: codex
  action: MINTED_TRAITMECH_ID
  changes: Added fungal appressorium formation with four primary-source snippets,
    a provenance-qualified Guy11 example and explicit morphology, terminology and
    mechanism boundaries. Ignored-and-hidden searches found only research leads, not
    an exact live trait. Reserved METPO:1061200 in v535; existing records unchanged
    and protein-level causal mechanism deferred.
  llm_assisted: true
- timestamp: '2026-10-07T05:45:55Z'
  curator: codex
  action: EVIDENCE_CORRECTION
  changes: 'Addressed #1774: attributed the Guy11 plastic-coverslip description to
    Methods and the conflicting hydrophobic-glass description to Results. Left the
    surface discrepancy unresolved; the verbatim snippet, formation phenotype and
    qualified canonical example remain unchanged.'
  llm_assisted: true